Link
to Family Description in DeltaGenera Included: Arceuthobium, Dendrophthora, Ginalloa, Korthalsella, Notothixos, Phoradendron, Viscum. The family is a well-supported, monophyletic group derived from Santalaceae.
Habit: Brittle "shrubs"
Parasitism: All aerial hemiparasites.
Roots: Modified into haustoria. The endophyte of the haustorium composed of a cortical strands (which are adjacent to the cambium) and sinkers (which penetrate to the xylem). In Arceuthobium, host is induced to form systemic or non-systemic witches' brooms.
Stem: Dichasially branched with nodal constrictions.
Leaves: Simple, opposite (decussate), entire, with silicified &/or sclerified mesophyll; stomates paracytic; exstipulate.
Inflorescence: Contracted dichasia, spikes. The dichasia are enfolded by a pair of fused bracts to form a bracteal cup. Dichasia may be sessile or borne on short peduncles. In monoecious plants, the staminate flower is usually centrally situated in the inflorescence while the pistillate flowers are arranged laterally. In dioecious plants, the staminate dichasia normally consist of three male flowers while the pistillate dichasia bear a solitary female flower in the bracteal cup.
Plant Sex: Monoecious, dioecious
Flowers: Small, unisexual, monochlamydous (with tepals),
epigynous.
Calyx: Tepals 3 in pistillate flowers or 4 (-6) in staminate flowers,
valvate; nectary disk present in staminate flowers
Corolla: Not present
Androecium: 3-4 stamens, opposite the tepals, adnate at the base,
filaments short (or absent - anther then sessile), anthers tetrasporangiate,
dithecal, opening by longitudinal slits or reduced to only two
sporangia and then opening by terminal pores or slits, or transversely
partitioned and opening by a number of transverse slits, or confluent
into a synandrium.
Pollen: Binucleate or trinucleate, triaperaturate, mostly spherical.
Gynoecium: Ovary inferior of 3-4 connate carpels, unilocular (or
solid with no locule owing to massive placenta called a mamelon);
style short, terminal or absent (hence stigma sessile).
Ovule: "Typical" ovule lacking; embryo sac embedded
in mamelon.
Embryo, etc.: Flower contains two, bisporic, 8-nucleate embryo
sacs; Allium type embryo sac development (Arceuthobium);
embryo with short suspensor.
Fruit: A berry containing one (sometimes two) seeds. May be explosive (Arceuthobium). Viscid layer inside the vascular bundles of the seed. Viscin composed on polysaccharide threads interspersed with mucillaginous pectic/mucopolysaccharide substances.
Seed: Testa lacking; embryo with one cotyledon, supposedly derived from a dicotyledonous state; endosperm chlorophyllous and starchy, derived from a primary endosperm nucleus of one of the embryo sacs; seeds typically with one or two embryos, although up to four may be present in one seed.
Chromosomes: X = 10-17; Base number for family perhaps 14.
Link
to Family Description in Delta